There is a well-known device that displays a state of a trolley wire for supplying power to a train in association with a display reference expressed in terms of, for example, kilometer. For the technique disclosed in Patent Literature 1, a wearing state of the trolley wire is calculated from an image captured by a line sensor. In accordance with the time of measurement of the trolley wire, then, the wearing state of the trolley wire is associated with kilometer information corresponding to positional information at the time of the measurement of the trolley wire, such that the wearing state of the trolley wire is displayed by the kilometer.